Abstract
Astrocytes play essential roles in the neural tissue where they form a continuous network, while displaying important local heterogeneity. Here, we performed multiclonal lineage tracing using combinatorial genetic markers together with a new large volume color imaging approach to study astrocyte development in the mouse cortex. We show that cortical astrocyte clones intermix with their neighbors and display extensive variability in terms of spatial organization, number and subtypes of cells generated. Clones develop through 3D spatial dispersion, while at the individual level astrocytes acquire progressively their complex morphology. Furthermore, we find that the astroglial network is supplied both before and after birth by ventricular progenitors that scatter in the neocortex and can give rise to protoplasmic as well as pial astrocyte subtypes. Altogether, these data suggest a model in which astrocyte precursors colonize the neocortex perinatally in a non-ordered manner, with local environment likely determining astrocyte clonal expansion and final morphotype.
Highlights
Astrocytes play essential roles in the neural tissue where they form a continuous network, while displaying important local heterogeneity
Despite these advances concerning cortical astrogenesis, a consensus has failed to emerge on the following questions: whether cortical astrocyte subtypes are produced by predetermined progenitors, as suggested by some studies[22,32], or from nonspecified progenitors generating similar astroglial descent which locally adapt to their substrate, as recently shown in the Drosophila ventral nerve cord[33]; how stereotyped the composition and distribution of the descent of these progenitors is; and how they primarily invade the neocortex
Using the MAGIC Markers (MM) combinatorial labeling strategy[34] together with a new large volume chromatic multiphoton serial microscopy technique (ChroMS)[23], we performed multiclonal lineage tracing in the mouse cerebral cortex and analyzed large numbers of astrocyte clones issued from nearby cortical progenitors, marked prior to the start of gliogenesis and tracked over long periods of time
Summary
Multiplexed 3D imaging of cortical astrocyte clones. To determine how the astroglial tridimensional matrix is established during corticogenesis, we tracked astrocyte development with the MM strategy[34], which enabled us to analyze the clonal descent of multiple individual embryonic progenitors marked with combinations of fluorescent proteins (FP). To understand how the scattered arrangement of astrocyte clones observed above develops, we explored the expansion dynamics of sister cells This analysis was led in parallel to the ChroMS mapping presented above, by electroporating MM at E15 and analyzing astroglial clones displaying rare color markers at P4, P7, and P21 on serial brain sections (Fig. 3a). Electroporation of a Cre-expressing plasmid in transgenic CAG-Cytbow mice at P0 (which results in indelible labeling of ventricular progenitors like the integrative markers) labeled numerous colorexpressing cortical astrocytes, identified based on morphology as well as S100β and Aldh1l1 expression These included both pial and protoplasmic subtypes, the latter being observed in all cortical layers (Fig. 5h; Supplementary Fig. 6d, e). These progenitors seed the cortical parenchyma in a scattered manner, in contrast with the orderly cohorts of neurons that form sequential layers during the course of corticogenesis
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
